I've made this mistake before!
One would think that it would be more interesting to show progs over
erases when they overlap, since progs always subset erases and show more
detail. However, erases occur much more rarely and are usually followed
by progs, so when rendering is low resolution (ascii) it's easy for
progs to completely cover up all erase operations.
Prioritizing erases prevents this.
At least this nuance is better documented this time around.
Christopher Haster
2909da9c13